The invention relates to an engine compression brake device for an internal combustion engine of a motor vehicle, particularly a commercial vehicle.
An engine compression brake device is known from EP 2191106 B1, having a camshaft with at least one cam group, the same having at least one firing cam and at least one brake cam, having at least one cam follower which is functionally assigned to the firing cam and which is included for the purpose of actuating at least one gas exchange valve in firing mode, and having a cam follower which is functionally assigned to the brake cam and which is included for the purpose of actuating the at least one gas exchange valve in the braking mode, and having a switchover device which is included for the purpose of switching between the firing mode and the braking mode.
The invention particularly addresses the problem of reducing costs for an engine compression brake device and/or reducing the consumption of an internal combustion engine having such an engine compression brake device.
The invention proceeds from an engine compression brake device, having at least one camshaft with at least one cam group, the same having at least one firing cam and at least one brake cam, having at least one cam follower which is functionally assigned to the firing cam and which is included for the purpose of actuating at least one gas exchange valve in firing mode, and having a cam follower which is functionally assigned to the brake cam and which is included for the purpose of actuating the at least one gas exchange valve in braking mode, and having a switchover device which is included for the purpose of switching between the firing mode and the braking mode.
It is suggested that the switchover device is included to convert a camshaft torque into a force for switching between the firing mode and the braking mode. As a result, it is possible to utilize the torque and/or the rotational movement of the camshaft, such that there is no need for an actuator mechanism which supplies the force for the switchover, by way of example in the form of hydraulic pressure. Because the torque and/or the rotational movement of the camshaft is used for the switchover, there is no need for additional actuators which fundamentally generate an additional drag torque, such that it is possible to increase the efficiency of an internal combustion engine having such an engine compression brake device. In particular, the consumption of an internal combustion engine can be reduced as a result. However, particularly since there is no need for a corresponding actuator mechanism which directly provides force for the switchover, it is possible to reduce the number and/or complexity of actuators, thereby achieving a particularly inexpensive design. The term “cam group” is used to mean a group of cams which includes all the cams of the camshaft for a working cylinder of the internal combustion engine. The term “firing mode” is used to particularly mean a control of the gas exchange valves for combustion operation. The term “braking mode” is used to particularly mean a control of the gas exchange valves for braking operation, wherein a compression work within the working cylinder is used for the braking operation. The firing mode and the braking mode particularly differ in the activation times for the gas exchange valves. The term “switchover device” in this context is particularly used to mean a mechanism which is provided for switching between the firing mode and the braking mode. The term “provided” is particularly used to mean specially designed and/or equipped.
It is further suggested that the switchover device has at least one slotted element connected to the camshaft in a torque-proof manner which allows an axial sliding movement, the slotted element having at least one guide slot which is provided for converting a rotational movement of the camshaft into a linear switching movement of the slotted element. As a result, the rotational movement and therefore the torque of the camshaft can be easily used to switch the slotted element between two switch positions. The mechanical switching of the slotted element can then be converted into a switchover between the firing mode and the braking mode, such that it is possible to implement the switchover device with only mechanical components. An actuator required to initiate the switchover can be designed in the form of a simple electric or electromagnetic actuator.
The engine compression brake device preferably includes an actuator which is fixed in relation to the slotted element and which has at least one switch pin, which is provided to engage in the at least one guide slot and convert the rotational movement of the camshaft into the linear switching movement of the slotted element. This allows the actuator to have a simple, cost-effective design. In particular, the actuator need only be provided for the purpose of bringing the switch pin into engagement with the switching gate. The shifting force required in this case is much lower than a supporting force which is necessary when the actuator switches directly between the firing mode and the braking mode—for example, by acting directly on the cam follower. The actuator only needs to be supplied with current for the switchover between the firing mode and the braking mode. It is possible to dispense with an actuator which must be continuously active during the braking mode and/or the firing mode to maintain the switched state of the firing mode or the braking mode.
In addition, it is suggested that the switchover device has a rocker arm bearing which has a first terminal position functionally assigned to the firing mode, and a second terminal position functionally assigned to the braking mode. This allows a particularly simple mechanical design for the switchover device. Because of such a configuration, it is possible for the terminal position of the rocker arm bearing to determine whether the firing mode or the braking mode is selected, such that only the rocker arm bearing needs to be switched from one terminal position to the other terminal position to accomplish the switchover. This makes it possible to realize the switchover simply using mechanical means, without the switchover requiring an additional actuator, such that a simple and robust switchover device is required. The term “rocker arm bearing” is used to particularly mean a bearing for rocker arms used for actuating the gas exchange valves, which is designed to receive and redirect actuation forces acting on the rocker arm when the gas exchange valves are actuated.
In one particularly advantageous embodiment, the engine compression brake device has at least two rocker arms, each of which comprises one of the cam followers, which are able to pivot about a rocker arm axis determined by the rocker arm bearing for the purpose of actuating the gas exchange valve. By connecting the rocker arm to the rocker arm bearing which can be switched between the first terminal position and the second terminal position, the one rocker arm or the other rocker arm, depending on the terminal position, can have a functional connection to the camshaft, such that it is possible to easily switch between the firing mode and the braking mode.
The rocker arm bearing is preferably designed to be switched by means of the torque of the camshaft between the two terminal positions. As a result, it is possible to utilize the torque of the camshaft, thereby achieving high efficiency. Preferably, the actuating forces acting on the rocker arms when the gas exchange valves are actuated are redirected to the rocker arm bearing in such a manner that a torque is applied which can be utilized for the switching from the one terminal position to the other terminal position.
The switchover device advantageously has at least one spring-loaded detent element which is designed to fix the rocker arm bearing in the two terminal positions. This makes it possible to support the actuating forces applied to the rocker arm bearing in the firing mode and the braking mode without the need for an actuator to be continuously active. This achieves particularly high efficiency.
It is also suggested that the switchover device has at least one detent contour element mounted to allow movement, wherein the at least one detent element of the rocker arm bearing is supported against the same. Because the detent contour element is mounted to allow movement, the terminal position lock of the rocker arm bearing can be easily released. At the same time, forces which are necessary for releasing the detent element can be significantly less than forces which can be supported by the detent element for fixing the rocker arm bearing. As a result, the rocker arm bearing can be secured via the detent element against strong actuating forces, while at the same time the secured position of the rocker arm bearing can be easily released.
It is further advantageous if the detent contour element has at least two locking positions, and the slotted element is provided to pivot the at least one detent contour element from the locking positions into at least one intermediate position between the locking positions. As a result, the torque and the rotational movement of the camshaft can be utilized to release the secured position of the rocker arm bearing, whereby the complete switchover between the firing mode and the braking mode is achieved by the torque and the rotational movement of the camshaft, and the actuator of the engine compression brake device is only provided for initiating the switchover.
In addition, it is suggested that the slotted element has two switch positions, and has an actuating pin which is designed to switch the at least one detent contour element from the first locking position into the intermediate position when in the first switch position, and from the second locking position into the intermediate position when in the second switch position. In this way, the slotted element can be mechanically coupled to the detent contour element in a particularly simple manner, thereby particularly achieving a configuration in which the detent contour element is switched at a defined camshaft position, such that the complete switchover can be adapted to a cam profile of the brake cam and/or the firing cam.
The switchover device can also be in used in principle in conjunction with other valve operating mechanisms. For example, the switchover device can be designed for switching between partial load operation and full load operation, rather than for switching between a firing mode and a braking mode. It is also conceivable that the switchover device is designed for switching between a firing mode and a decompression mode, for example to increase comfort during a start and a stop of an internal combustion engine.
As a further idea of the invention, a valve operating device is therefore suggested, having at least one camshaft which comprises at least one cam group with at least one first cam and at least one second cam, having at least one cam follower functionally assigned to the first cam, which is provided for actuating at least one gas exchange valve in a first mode, and having a cam follower functionally assigned to the second cam, which is provided for actuating at least one gas exchange valve in a second mode, and having a switchover device which is provided to switch between the first mode and the second mode, wherein the switchover device is provided for the purpose of converting a torque of the camshaft into a force for switching between the first mode and the second mode. Further possible embodiments in this context particularly correspond to the dependent claims.
Additional advantages are found in the following description of the figures. The figures illustrate an embodiment of the invention. The figures, the figure description, and the claims contain numerous features in combination. A person skilled in the art will also expediently consider the features individually and combine them into additional, practical combinations.